JPS5936823B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to thermal compression gang bonding of semiconductor devices, and more particularly to thermal compression gang bonding between copper and gold portions of structures for interconnecting semiconductor devices to circuits used. related to thermocompression gang bonding.

Such connection structures include, for example, lead frames, interconnect leads, and gang bonding bumps on semiconductor devices.

Conventionally, thermocompression gang bonding of semiconductor devices has been accomplished.

In these conventional connections, the copper pattern of the wire-like interconnect leads is plated with a nickel layer, which is 0.762 to 1.524 microns (30 to 60 microns).
It is plated with gold to a thickness within the range of microinches. The gold-plated interconnect ribbon leads are thermocompression gangs supported from the surface of the semiconductor device and then bonded to gold keying bonding rings that rise above it. During the thermocompression gang bonding step, the nickel layer acts as a diffusion barrier under the gold layer so that a gold-to-gold bond is obtained between the gold plated copper interconnect leads and the gold gang bond bumps. A similar gold-to-gold thermocompression bond is obtained between the gold-plated interconnect leads and the gold-plated lead frame at the outer ends of the interconnect leads. One of the problems with this gold-to-gold thermocompression bonding technique is that it is expensive due to the cost of the gold used in making the bond.

A primary object of the present invention is to provide an improved method for thermocompression gang bonding lead structures to semiconductor devices.

In one aspect of the invention, the copper portions of the structure for interconnecting the semiconductor device to the circuit used are capable of solid-state diffusion of the copper portions into the gold portions and upon cooling. A thermocompression gang bonded to the gold portion of another such interconnect structure to obtain a bonding interface between the copper and gold portions; Become.

In another feature of the invention, the gold portion hot compression bonded to the copper portion comprises a layer of gold on the steel member, and the diffusion barrier layer is disposed between the gold layer and the copper member. In yet another feature of the invention, the gold layer on the leadframe structure is heat compression bonded to the copper interconnect leads.

In another feature of the invention, the inner ends of the copper interconnect lead structures are bonded to the gold portions of the gang bonding bumps by thermocompression bonding therebetween.

1 and 2, a bonding tape 11 is shown for use in an automatic thermocompression gang bonding machine for attaching interconnect leads to a die.

Tape 11 includes a wrought copper sheet 12 that is perforated at 13 along each edge to receive a sprocket drive wheel for advancing the tape from a supply reel through an automatic gang bonding machine. A plurality of interconnecting ribbon lead patterns of metal foil 14 are formed in wrought copper foil 12, with a typical pattern shown in FIG. A polyimide resin film 15 is secured to the underside of the copper sheet 12 to hold the interconnect lead portions 16 of the pattern 14 in the desired position. A rectangular central hole 18 is provided in the film 15 with the inner ends of interconnecting ribbon leads 16 extending above the lip of the rectangular hole 18. A plurality of openings 19 are placed around each of the interconnect lead patterns 14 to facilitate cutting of the foil 12 and film 15 in the next step of the bonding process. 3 and 4, a die or semiconductor chip 2 is shown.
A portion of a die bonding machine is shown for thermocompression gang bonding of the inner ends of interconnect leads 16 to a plurality of gang bonding bumps 21 disposed around the periphery of the interconnect leads 16 .

The individual chip 22 includes a semiconductor substrate portion 23 with an epitaxial layer grown thereon.
It has a shaped conductive area 24.

A plurality of p+ conductive regions 25 are diffused into n region 24. An n+ conductive region 26 is diffused into the n-evitaxial layer 24 to make electrical contact thereto. The upper surface of n-layer 24 is covered with a passivation layer 27, such as silicon dioxide. A plurality of holes 29 are provided in silicon dioxide layer 27 in alignment with some of regions 25 and 26. An interconnect metallization pattern 28, such as made of aluminum, is provided above the silicon dioxide layer and through the hole 29 to make electrical contact to the n+ and p+ type regions.

In some areas, the gigantic bonding bumps 21 are placed on the interconnect metallization pattern 28, for example by electroplating, and electrical contacts are made thereto. In a typical example, the gang bonding bump 21 has a thickness of 1 to 2
mill and has a cross section of approximately 12 square mils at the base. In other areas of the semiconductor die 22, the interconnect metallization pattern 28 is covered with a second vacillation layer 31, such as silicon dioxide. Glass plate 3 via high temperature film 34 bonded to plate 33
Supported by 3.

The die is supported from film 34 through a layer of release wax 36. This assembly is scored by serrations 37 passing through the release wax and partially into the hot film 34. The die bonding machine separates the individual chips to be bonded 2
2 is aligned with a die bonding tool 38, such as carbon, which is heated to a temperature of, for example, 550° C. for gigantic bonding.

The bonding tool 38 applies approximately 1009 bumps per square millimeter or 1.24 per square millimeter for a period of approximately 0.2 seconds.
interconnection leads 16 downwardly towards the upper end of gang bond bump 21 at a pressure of
Pressurize the inner end of the Typically, the bonding tool 38 applies pressure to the guyang bond and the guyang bonding bump simultaneously. Each gigantic bonding bump 21 includes a relatively thin base layer portion 39 of copper harder than 50 KnOOp.

A layer of gold 41, such as 0.381-1.52 microns (15-60 microinches) thick, is provided over the copper layer 39, and a diffusion barrier 40, such as nickel, is provided over the gold layer 41.
and the lower copper layer 39.

In a typical example, the gold layer 41 to be thermocompression bonded is 15 microinches thick.
Above, preferably 0.762 to 1.52 microns (30
~60 microinches). The nickel layer is 2.54-17.8 microns (0.1-0.
7 mil), and the total thickness of bump 21 is 7.62
~50.8 microns (0.3-2.0 mils). The copper interconnect leads 16 are preferably very thin, such as gold, copper, phosphate, chromate, etc. so that thermocompression bonding can be made through the very thin anti-oxidation layer 42. Covered with an antioxidant coating. Copper-to-gold thermocompression bonding involves bonding the inner ends of the copper interconnect leads 16 with the thermocompression bonding by compressing the copper leads into thermocompression bonding engagement with the gold layer 41, as described above. A solid-state diffusion of copper from the interconnect lead 16 is obtained in the gold layer 41 of the young bonding bump 21, so that upon cooling, the copper and gold portions A bonding interface between the two is provided, which consists of a solid state diffusion of copper into the gold portion.

Diffusion barrier 40 serves to prevent diffusion of copper from layer 39 into gold layer 41 due to heating of the gold layer by thermocompression bonding tool 38 .

Further, the diffusion barrier layer 40 is connected to the copper layer 3 through the gold layer 41.
Prevent copper diffusion into 9. The resulting copper-to-gold thermocompression bond is even stronger than copper-to-copper or gold-to-gold thermocompression bonding. In addition, copper-to-gold bonding does not require interconnect leads 16 to be plated with a diffusion barrier (unlike prior art gold-to-gold bonding) and does not need to be plated with a relatively thin layer of gold. It can be made with significantly less material and processing cost than traditional gold-to-gold bonding. As an alternative to using a gold layer or cup 41, the entire bump 21 may be made of gold, with a copper-to-gold thermocompression bond made to the gold layer 41 in the same manner as a thermocompression bond.

Once the die 22 is gang bonded to the inner edge of the interconnect lead pattern 16 by heating the die with the thermocompression bonding tool 38, the wax releases the die, thereby bonding the die to the copper sheet or table 12. be transported.

The die-attached tape 12 is fed to a second machine that heat compression bonds the outer portions of the interconnect leads 16 to the inner ends of the lead frame member 43 (FIGS. 5 and 6). If the lead frame 43 is made of copper, it is first plated with a barrier layer material 44, such as nickel, and then selectively plated with a layer of gold 45, to which the copper interconnect leads 16 are heat compression bonded. be done. The upper surface of the interconnect leads 16 that are bonded to the selectively plated gold layer 45 are preferably thin enough to allow thermocompression bonding, such as gold, chromate or copper phosphate. coated with an anti-oxidant coating. The thermocompression bonding tool 46 is adapted to press the upper surface of the interconnect lead 16 upwardly toward the underside of the interconnect lead 16 into engagement with the lower surface of the gold layer 45 .

In a typical example, the temperature of the bonding tool 46 is 45
0° C. and is held in engagement with interconnect lead 16 for approximately 1.5 seconds. The joining pressure per square millimeter is
Typically, about three times the pressure used to bond the inner ends of interconnect leads 16 to gigantic bonding bumps 21, or 1.55 per square millimeter.
~4.64 x 104 grams (10-30 grams per square mil). The selective gold plating layer 45 interfaces with the interconnect leads 16 and has an area of, for example, 0.145 square millimeters (225 square millimeters). The bond strength achieved between the gold layer 45 is typically greater than 509 and the lead frame 43 and the interconnect leads 1
0.145 square millimeters (22
As high as 2009 for a thermally compressed copper-to-gold interface supporting area of 5.5 square mils). Lead frame 43
After bonding to interconnect leads 16, the lead frame is mounted in a molded epoxy package 48 as shown in FIG. When thermocompression bonding is done between the interconnect leads 16 and the inner ends of the lead frame 43, the copper interconnect lead pattern 1
4 is cut along the line of perforation 19, thereby transferring lead attach die 22 from table 11 to leadframe structure 43.

Another embodiment of the invention is shown in FIG. 7, in which the lead frame 43 is made of nickel alloy 42 or KOvar.
made from.

In such a case, the gold layer 45 preferably has a thickness of 1
．． A thickness in the range of 50-60 microinches is plated directly onto the lead frame 43 in selected areas as described above. As mentioned above, the copper interconnect leads 16 are preferably coated with an anti-oxidant coating, and this member is brought into hot compression bonding relationship as described in connection with FIG. 45 and copper interconnect leads 16 to obtain thermal compression bonding. An advantage of using the copper-to-gold thermocompression bonding of the present invention for gang bonding lead structures to semiconductor devices is that relatively inexpensive copper components can be used with relatively expensive gold layers or bumps. There it is.

The gold portions may be confined to the bumps and selected areas of the lead frame 43, thereby minimizing gold usage and component cost. Additionally, a stronger bond can be obtained than conventional gold-to-gold or copper-to-copper bonding.

[Brief explanation of drawings]

FIG. 1 is a plan view of a film-shaped gang bonding tape having a metal interconnect lead pattern for thermal compression bonding to a semiconductor chip or die by an automatic gang bonding machine; FIG. An enlarged plan view of a portion of the structure of FIG. 1 represented by lines; FIG. 3 is an enlarged view of a thermocompression die bonding head for gang bonding an interconnect lead structure to a semiconductor chip or die; A cross-sectional view, FIG. 4 is an enlarged detail of a portion of the structure of FIG. 3 represented by line 4--4, and FIG. 5 shows an integrated circuit die or chip mounted on a lead frame structure. FIG. 6 is a cross-sectional view of an integrated circuit package having 6-
6 is an enlarged detail of a portion of the structure of FIG. 5 represented by line 6; FIG. 7 is an enlarged detail of a portion of the structure of FIG. 6 represented by line 7-7; FIG. 3 is a detailed diagram of the embodiment. In the figure, reference numeral 16 indicates the copper metal interconnection lead, and reference numeral 41 indicates the gold layer of the gigantic bonding bump 21.

Claims (1)

[Claims] 1 a semiconductor chip means, a lead frame means, and a metal interconnect means, the semiconductor chip means comprising an interconnect metallization pattern and an interconnect metallization pattern for making electrical connections to various different areas of the semiconductor chip means; a plurality of gang bonding metal bumps raised from the surface of the semiconductor chip means and connected at bases to the interconnect metallization pattern, the lead frame means being connected to other circuit devices using the semiconductor device; said metal interconnection means being adapted to electrically connect to at least one said gang bonding bump through a bonding interface comprising a solid state diffusion of copper from a copper portion to a gold portion of said gang bonding bump. A semiconductor device having a copper portion bonded to a gold portion of the semiconductor chip means and electrically interconnecting the gang bonding bumps of the semiconductor chip means to the lead frame means.